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Bull Thistle

Cirsium vulgare

Summary 8

Cirsium vulgare (Spear Thistle) is a species of the genus Cirsium, native throughout most of Europe (north to 66°N, locally 68°N), western Asia (east to the Yenisei Valley), and northwestern Africa (Atlas Mountains). It is also naturalised in North America and Australia and is as an invasive weed in some areas.

Description 9

More info for the terms: forb, litter, monocarpic, phase

The following description is based on reviews by Beck [15], Klinkhamer and de Jong [80] and Forcella and Randall [50]. It presents characteristics of bull thistle that may be relevant to fire ecology, and is not meant to be used for identification. Keys for identifying bull thistle are available (e.g. [28,53,56,84,161]). A detailed description of the biology of bull thistle is given by Klinkhamer and de Jong [80].

Bull thistle is a biennial, and sometimes annual or monocarpic perennial, forb. In the juvenile phase, individual bull thistle plants form a single rosette with a taproot up to 28 inches (70 cm) long. Rosettes may develop up to 3.3 feet (1 m) in diameter. The taproot does not spread, but develops several smaller lateral roots. Stems have spiny wings and grow 1 to 6.6 feet (0.3 to 2 m) tall, with many spreading branches, and sometimes a single stem. Bull thistle stem leaves are more or less lance-shaped and 3 to 12 inches (7.6-30 cm) long, prickly hairy on the top and very hairy underneath. Lobes on leaves are tipped with stout spines. Bull thistle flowerheads are 1.5 to 2 inches (3.8 to 5 cm) in diameter, 1 to 2 inches (2.5-5 cm) long, usually solitary, and more or less clustered at the ends of shoots and branches. Flowers are subtended by narrow, spine-tipped bracts. Bull thistle fruits are achenes, 1/16th-inch (0.15 cm) long, with a long, hairy plume that is easily detached.

The litter of Cirsium species is said to inhibit the growth of other plants. In bull thistle, this is probably a result of the immobilization of nutrients during the process of litter breakdown [80]. Descriptions of mycorrhizal associations in bull thistle [17,62] and their positive effects on its growth [163] are available.

Habitat 10

This thistle thrives in a wide variety of habitats, such as rough grassland, overgrazed pasture, dunes, and sea-cliffs. It also occurs in fertile habitats subject to disturbance, including waste ground, arable fields, spoil heaps, and on burned areas of woodland (3). As it has been discovered in pre-Neolithic deposits, it seems that spear-thistle does not require human disturbance to prosper (1).

Successional status 11

More info on this topic.

More info for the terms: cover, eruption, succession, wildfire

Bull thistle is an early successional species that establishes well in open, disturbed sites, and is an important weed in clearcuts and conifer plantations in the western U.S. [128]. Examples where bull thistle is reported as an early successional component and sometimes dominant after timber harvest (with and without burning) include studies in California [95,97], Oregon [27,45,60,104], Idaho [57,72,141], Montana [4,5,137], and Michigan [29,85]. Bull thistle is 1 of several species of Asteraceae that often become prolific immediately after fire in southern Tasmania, Australia [10], and was a common component in study plots following wildfire and suppression efforts in Glacier National Park in the fall of 1988 [16]. Bull thistle was also among the pioneering species in primary successional habitats on Mount St. Helens following the eruption in 1980 [150]. It is a common component on repeatedly disturbed sites such as roadsides [114] and grazed pastures. In Australia bull thistle populations persisted for 4 years in grazed pasture but declined in ungrazed pasture, suggesting that grazing allowed bull thistle populations to thrive [49].

Populations of bull thistle tend to be short lived, establishing after disturbance, dominating for a few years, and then declining as other vegetation recovers [27,33,41,95,96,155,167]. Few bull thistle plants can be found in undisturbed clearcuts and plantations older than 8 years [128], although some plants may remain for longer periods. After clearcutting of subalpine fir in western Montana, bull thistle cover peaked after 3 years, was still present after 17 years, but was not present on undisturbed sites or 1-year-old cuts [92]. Bull thistle was present 7 to 16 years after clearcutting in grand fir in western Montana, but absent from adjacent uncut forest [2]. Bull thistle was the most frequent species observed 6 to 9 years after clearcutting in Sierra Nevada mixed conifer [1]. The  peak distribution of bull thistle in German old fields is 3 to 4 years following disturbance [80]. Specific patterns of succession are described for Douglas-fir and ponderosa pine forests in California and Oregon [98] and for burned Douglas-fir clearcuts in the Coast range of western Oregon, where bull thistle is the dominant species the 2nd year after clearcutting [131].

True biennials are uncommon or absent in late successional plant communities because they often need abundant light for establishment [50]. Doucet and Cavers [41] note that bull thistle is absent from densely shaded areas. A review by Klinkhamer and de Jong [80] indicates that bull thistle is almost absent if light is reduced to less than 40% of full sunlight. Bull thistle invasion is enhanced in pastures with decreased vegetative cover [49]. In a greenhouse experiment, bull thistle germination was not suppressed by sedge (Carex spp.) cover, but subsequent survival of seedlings was reduced and the percentage of seeds that germinated and survived decreased exponentially with increasing cover [121]. In Dutch coastal dunes, however, bull thistle was more restricted to shaded sites [34].

Threats 12

Comments: A difficult-to-control exotic in the US.

Sources and Credits

  1. (c) beautifulcataya, some rights reserved (CC BY-NC-ND), http://www.flickr.com/photos/70668033@N00/3804996777
  2. (c) Elaine with Grey Cats, some rights reserved (CC BY-SA), https://www.flickr.com/photos/elainegreycats/14518107967/
  3. (c) Harry Rose, some rights reserved (CC BY), https://www.flickr.com/photos/macleaygrassman/12401009905/
  4. (c) Fotorus, some rights reserved (CC BY-ND), https://www.flickr.com/photos/fotorus/13154733414/
  5. (c) Sciadopitys, some rights reserved (CC BY-SA), https://www.flickr.com/photos/40183553@N02/5909026723/
  6. (c) NY State IPM Program at Cornell University, some rights reserved (CC BY), https://www.flickr.com/photos/99758165@N06/18653364159/
  7. (c) NY State IPM Program at Cornell University, some rights reserved (CC BY), https://www.flickr.com/photos/99758165@N06/18651784838/
  8. Adapted by Kate Wagner from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Cirsium_vulgare
  9. Public Domain, http://eol.org/data_objects/24628178
  10. (c) Wildscreen, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/6688838
  11. Public Domain, http://eol.org/data_objects/24628182
  12. (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/29002212

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